Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $118.73   5.857%   $125.684   $125.68   $125.70   $125.70  
  Purchase #2 $33.92   10.801%   $37.5837   $37.58   $37.60   $37.60  
  Purchase #3 $33.68   9.806%   $36.9827   $36.98   $37.00   $37.00  
  Purchase #4 $163.77   10.479%   $180.9315   $180.93   $180.95   $180.90  
  Purchase #5 $150.60   3.319%   $155.5984   $155.60   $155.60   $155.60  
  Purchase #6 $182.62   4.355%   $190.5731   $190.57   $190.55   $190.60  
  Purchase #7 $60.96   12.527%   $68.5965   $68.60   $68.60   $68.60  
  7 purchase totals = $744.28       $795.9499   $795.94   $796.00   $796.00